This study investigates the crystalline quality, surface, and optical properties of semi-polar GaN (11 (2) over bar 2) grown on m-sapphire substrates with and without a CrN interlayer using molecular beam epitaxy (MBE). The results of the characterization performed by an X-ray diffraction system, scanning electron microscopy and photoluminescence system, all indicate that the crystalline quality, threading dislocation, surface morphology and optical properties of (11 (2) over bar2) GaN grown with the CrN were superior to those when CrN was not inserted. Details of defect-related emissions of these two samples were observed and investigated in temperature dependent PL measurements, with a low temperature PL spectrum. A weak basal stacking fault related (BSF-related) emission at 3.432 eV was observed in these two samples. In comparison, the BSF-related emission peak as a shoulder to the near band edge (NBE) peaks for the semi-polar GaN grown without CrN was hardly distinguishable at a low temperature. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3615957] All rights reserved.